Plotting script for Matlab/Octave

zplane3d

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Incorporates region of convergence and unit circle into 3D plot and also plots 2D zplane and frequency response (through regular Matlab/Octave functions zplane and freqz). Heavily commented so have a look around the code.

Set transfer function numerator and denominator coefficients at the top of the script. (Just edit the script directly)

\[X(z)=\frac{2+z^{-1}}{1-z^{-1}-2z^{-2}}\]

Enter

b = [2  1  0];
a = [1 -1 -1];
causal = true;

Set causal to false for ROC inside circle instead of outside.

Or easier to set poles as factors

\[X(z)=\frac{(z+0.5)}{(z+2)(z-1)}\]

Enter:

b  = [1  0.5];
a1 = [1  2];
a2 = [1 -1];
a = conv(a1, a2);
causal = true;

Some examples

Simple example

b = [1  0];
a = [1 -1];
causal = true;

Simple example View large image

First example above

b = [2  1  0];
a = [1 -1 -1];
causal = true;

First example above View large image

Factors example above

b  = [1  0.5];
a1 = [1  2];
a2 = [1 -1];
a = conv(a1, a2);
causal = true;

Factors example above View large image

Complex numbers example

b  = [1  (1+j)];
a1 = [1  2];
a2 = [1 -0.75];
a = conv(a1, a2);
causal = false;

Complex numbers example View large image